A NESL is a set of libraries for Silverlight developers that allow them to access some really cool features of Windows 7 from their Silverlight applications.
- Take advantage of sensors like accelerometers, light sensors, compasses, GPS etc.
- Access content from connected portable devices like music players and digital cameras.
- Capture and create video from webcams and screen output
- Use speech recognition and text to speech capabilities.
- Integrate with the Windows 7 taskbar (Jump Lists, Icon Overlays, Taskbar Progress etc.)
- And more!
Head over to http://code.msdn.microsoft.com/nesl to start developing with it.